Conventionally, for sensing a capacitance of a capacitor, the capacitor is first charged to a certain voltage and then shunt to a reference capacitor for charge balance therebetween, by which the amount of charges transferred to the reference capacitor can be used to calculate the capacitance of the sensed capacitor based on the capacitance of the reference capacitor. However, this method requires to wait for a long time before the charge balance process finishes, and is thus applied only to the circuits with slower response speed.
For some applications, there is a need of a circuit and method for sensing a capacitance with faster response speed.